Constant Revving at ~2000rpm...
 

Hey guys my 90 miata 1.6L is constantly revving at around 2k rpms when in neutral even when fully warmed up. A while ago I got an engine light for 3 codes: a) coolant thermistor(if i remember correctly)
b) oxygen sensor reading too high
c) oxygen sensor reading stays the same

I actually haven't seen these codes in a long time so can't remember exactly what they were, but that is the general idea.
So does anyone have any clue on what's up with those rev's? :confused:

large vacuum leak.

iac valve malfunction?

Has your vacuum at idle changed? If so, it probably is a vacuum leak.